Heat sensitive printing element and method



June 12, 195] MURRAY I 2,556,550

HEAT SENSITIVE PRINTING ELEMENT AND METHOD Filed Feb. 27, 1947 4 Sheets-Sheet 1 FIG. 1. 33 {1K 34 IJDDDE] EDGE A LEX4NDER M URR4Y INVENTOR ATTORNEY C9 AGENT A. MURRAY HEAT SENSITIVE PRINTING ELEMENT AND METHOD 4 Sheets-Sheet 2 FIG..9.

ALEXANDER MURRAY INVENTOR W BY ATTORNEY AGENT June 12, 1951 Filed Feb. 27, 1947 June 12, 1951 MURRAY 2,556,550

HEAT SENSITIVE PRINTING ELEMENT AND METHOD 4 Shegts-Sheet 3 Filed Feb. 27, 1947 FIG.11.

FIG. 12 F J30 'T 4 139 '1 ii f 131 \l??fi \f\ FIGJS. 156 5% 150 %V S 149 1 16.14. 151 152 14 1 1 (1 1 (I 2 i" FIG. 16.

FIGJ7.

ALEXANDER MURRAY ATTORNEY 43 AGENT I N VENTOR A. MURRAY HEAT SENSITIVE PRINTING ELEMENT AND METHOD Filed Feb. 27, 1947 J me 12, 1951 4 Sheats-Shet 4 FIG.1 9.

1 L 2 0 Q m m miiL m a a 1 a f 41 a 2 A u m v n n u u n 4 LITILli iL /H m mm M um M r H R m E w w m Y Patented June 12, 1951 HEAT SENSITIVE PRINTING ELEMENT AND METHOD Alexander Murray, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application February 27, 1947, Serial No. 731,173

Claims. 1

This invention relates to photo reproduction and particularly to processes and apparatus for producing a fairly large number of prints.

Straight photographic processes are inefficient and unnecessarily expensive when the number of reproductions exceeds 100 or 200, particularly in the case of color reproductions. On the other hand, photoengraving and photolithographic methods of color reproduction require expensive equipment whose cost is not warranted unless the total number of reproductions exceeds 5,000 or 10,000, say, in each case. The primary object of the present invention is to provide a process and apparatus for efficiently producing reproductions, particularly color reproductions, where only 1,000 or 2,000 prints are required. Adequately to satisfy the large market for such a printing process, the process itself must be a rapid and relatively inexpensive one. Of course the invention is applicable even when the number of prints required is larger or smaller than this particular range.

A further object, particularl of certain embodiments of the invention, is to provide a printing process in which coloring material is applied directly to paper, either as a halftone pattern or as a continuous tone pattern, in accordance with a continuous-tone negative or positive transparency without the intermediate step of making a'halttone negative.

The various embodiments of the invention described below and in co-pending applications referred to below, have individual advantages such as simplicity, rapidity and ease of operation, etc., each of which constitutes an object of the invention.

According to the invention a picture to be reproduced is scanned by a line proceeding sideways over the whole area of the picture at once in counter-distinction to ordinary scanning procedures in which a dot scans the picture a line at a time. It is well known that quality reproduction of pictures requires a certain number or" lines per inch distinctively reproduced, but the number of lines depends on the size of the picture. For example, there is no point in using a lineness of 150 lines per inch in the production of a billboard. For the sake of definiteness, a limit of acceptable quality will be here taken as that represented by 50 lines in the total width of the picture. Fewer lines is considered inacceptable for most purposes. The line which scans the picture according to the invention, is made up of at least 50 small juxtaposed photosensitive elements, and the direction of scanning is at an angle, either a right angle or an acute angle, to this scanning line. The picture to be reproduced will be either a positive or a negative record, the

final reproduction being a positive, of course. The term reproducing is intended to mean both the production of a positive from a positive, or the production of a positive from a negative. The line of elements is, of course, made up of discrete and usually slightly separated elements. Just as there is an equivalence between contact and projection printing in photography, the scanning may be by projection through an optical system or by having the elements efiectively in contact with the record. Each element of the scanning line produces a track and, in accordance with the above definition of minimal quality and definition, the width of each track must be less than two per cent of the width of the picture. Furthermore, the total width of all the scanning tracks must be at least equal to the width of the picture in order to encompass the whole picture by a single scanning operation.

synchronously with the scanning of the picture, an image receptive sheet, such as a sheet of paper to receive ink or a photosensitiv layer, is scanned with a corresponding number of juxtaposed density control elements. When this invention is applied to the making of enlarged pictures, for example, the density control elements are considerably larger than the photosensitive elements which scan the picture, but there is still a one for one correspondence between density control elements and photosensitive elements. Each density control element may be a valve or other means for controlling the deposition of ink, or it may be a valve for controlling the quantity of radiant energy falling on a sensitive medium. In accordance with the invention, each density control element is operated according to the response of the corresponding photosensitive element. In this way, a whole picture is scanned in a single sweep and a single print is made relatively rapidly. Thus there is eliminated one of the main objections to prior scanning processes in which the picture is scanned a line at a time.

It is not necessary that the scanning be exactly at right angles to the lines of elements, and it is preferably at an acute angle since an oblique arrangement of the photosensitive elements simplifies the manufacture in some instances, especially when the elements are very small ones. Another embodiment of the invention having the same advantage of permitting easy manufacture of verysmall elements, employs a zig-zag line of elements. I

A preferred embodiment of the invention employs as its photosensitive elements small fluidcontaining cells, in which the expansion of the fluid in the cells controls the deposition of ink on a paper. A small capillary leads from each cell to the point at which the ink is deposited on the paper. In on form of this embodiment, the whole cell and capillary are filled with ink, but preferably the cell is filled with a gaseous medium or other material having a high coefficient of expansion, which material in turn forces the ink from the capillary.

Cross reference is made at this point to a photoelectric embodiment of the invention described in co-pending application, Serial Number 731,372, filed concurrentlyherewith, by C. Q. Glassey, now U. S. Patent 2,487,865. In another alternative a relief image is scanned by a line of tactile elements to control correspondin ink depositors or other density control elements. Reference is also made to an application of thermal expansion cells to printing a whole area at once rather than by scanning, which areal block is described in copending application, Serial Number 745,019, filed April 30, 1947, by C. Q. Glassey, now Patent No. 2,543,013 dated February 27, 1951. This latter case describes a number of methods of making expansion cells which may be used alternatively to the one described herein for either a line or an area of cells.

In the application of thermal expansion cells to the above described scanning arrangements, it is preferable to deposit one line of ink, either in halftone dots or with a controlled amount of spreading of the ink to give a continuous-tone effect, and then to refill the capillaries and to cool the cells before repeating the operation to print the next line. That is, the cells are arranged in a line onto which an image of the picture to be reproduced is projected, either by an optical system or by contact printing. The heat in the image is transferred to the cells differentially in accordance with the image, which heat causes the fluid in the cells to expand, forcing proportional amounts of ink from the capillaries onto the adjacent paper. The image is then out off momentarily, the cells are allowed to cool, the working pressure in the cells is reestablished, and the capillaries recharged with ink. During this interval the picture is moved the width of the scanning line, and the paper is correspondingly moved to receive the next line of ink depositions. The light is turned on by a suitable shutter arrangement for the necessary interval of time to deposit the ink properly, and then the whole cycle is repeated.

Obviously this line of cells is made up of very small cells, especially when there are 150 cells to the inch, for example. These cells may be made and assembled in various ways, but one particularly simple method involves formin a relief matrix, for example by electrodeposition on pre-determined areas, and then by stripping plastic sheets from this matrix with the cell structure incorporated as intaglio in the plastic.

Registration is always a problem in color printing processes, and in the present invention, it can be obtained by any of the usual careful methods used in other color printing processes. However, one particularly applicable system involves four-color printing simultaneously, two colors being printed on each side of a thin transparent pellicle, which may be later laminated to an opaque white support.

' Other advantages and features of the present invention will be apparent from the following description ,of various preferred embodiments thereof when read in connection with the accompanying drawings, in which:

Fig. 1 is a perspective view of one embodiment 4 of the invention which illustrates the general principles thereof.

Fig. 2 is an enlarged detail of one feature of Fig. 1.

Figs. 3 and 4 illustrate preferred arrangements of the line of elements in Fig. 1.

Fig. 5 is a greatly enlarged front view of elements according to a preferred embodiment of the invention.

Fig. 6 is a vertical cross-section of the same elements, also greatly enlarged.

Figs. 7 and 8 are respectively plan view and vertical section, both greatly enlarged of a slightly different embodiment of the invention.

Figs. 9 and 10 are respectively a greatly enlarged vertical section and a perspective View of a preferred embodiment of the invention.

Fig. 11 is a diagrammatic vertical section of an embodiment of the invention.

Fig. 12 similarly illustrates another embodiment of the invention.

Figs. 13 to 16 illustrate a preferred method of manufacturing expansion cells such as illustrated in Figs. 5 to 12. I

Fig. 17 is a greatly enlarged perspective view of a preferred arrangement of expansion cells for the invention.

Figs. 18 and 19 are respectively front and side elevations of a preferred form of printing press employing one embodiment of the invention.

Fig. 20 illustrates a detail of the carrier belt of Figs. 18 and 19.

For clarity, unessential details have been omitted from Fig. 1. In this figure a color transparency 33 is moved as indicated by the arrow 3|, by means not shown, under a triple scanning line provided by three lamps 32, red, green, and blue filters 33 and cylindrical lenses 34. The broken line 36 indicates the red line as focused on the transparency 30. The necessary light shields for confinin the scanning beams to their respective paths are not shown in the drawing since they wouldoconfuse the illustration. The light passing through the transparency 30 impinges on a row of photosensitive elements 38 which are shown as photoelectric or selenium cells manufactured in accordance with Serial Number 731,372, new U. S. Patent 2,487,865, Glassey, mentioned above. Alternatively, these photosensitive elements may be expansion cells as described in connection with Figs. 5 to 20 of the present application. For acceptable quality there should be at least 50 such cells in the total width of the transparency 30. 50 to lines per inch gives satisfactory reproduction for many purposes.

The reaction of the photosensitive elements 38 is used, according to the invention, to control the deposition of ink on a strip of paper 4!], which is moved as indicated by arrow 4| synchronously with the movement of transparency 30. This control of ink depositing elements 42 is illustrated schematically by connecting wires 43.

Various direct control arrangements for the ink depositing elements may be used, such as the differential heating of bi-metallic pen orifices in accordance with the current from photoelectric or selenium cells. However, I prefer to employ electrostatic repulsion of ink as illustrated in Fig. 2. Any ink whose vehicle has a relatively high electrical resistance is subject to electrostatic repulsion from a charged point. Many, if not most, inks have this property. In Fig. 2 the individual elements 46 are insulated from each other by insulating layers 41, and each element comes to a relatively sharp point 48'. The space 50 between the points is filled with ink and normally this ink is flush with the end of the points 48. The charge on the particular point 5|, however, is sufficient to repel some of the ink which thus forms a drop 52, which moves away from the point 5| and over to a layer 40 of paper which is carefully held just a short distance below the points 48. I prefer to operate this embodiment of the invention intermittently wherein a line of the transparency is scanned, the ink corresponding to that line is deposited, and then the whole press is reset to print the next line, the transparency being moved the width of one line, an inking member being applied to the pen points, and the paper to be printed being moved one line. As illustrated, the transparency 30 should be a negative in order to produce a positive final print. Continuous deposition is possible but adequate quality control is not so easily assured.

The manufacture of the photosensitive ele-' ments in a line is somewhat difiicult because of the small size of the elements, and therefore, it is preferable, as illustrated in Figs. 3 and 4, to have this line oblique or zig-zag. The width of the track scanned by each element is still the same size as it was,- but more space is provided around each element to permit greater rigidity of the supporting members. Both the oblique line and the zig zag line are still referred to as a line of elements, and the direction of scanning is said to be at an angle to this line. In Fig. 1 the direction of scanning is at a right angle, in Fig. 3, it is an acute angle, and in Fig. 4 it is alternately acute and obtuse having two values supplementary to each other.

A highly preferred embodiment of the invention makes the photosensitive elements and the density controlled elements as a single unit. The light responsive element is simply a small cell containing a fluid whose expansion under the radiant energy is the response of the element. As illustrated in Fig. 5, such a cell 69 is provided with a capillary 6| to an orifice 62 from which ink is ejected to deposit on the paper being printed. A plurality of such cells 6|] are juxtaposed, perhaps 150 to the inch, and each is provided with a heat absorbing cover 83. As before, it is preferable to employ intermittency in the scanning so that the ink cells are re-charged after each is printed. A simple arrangement for doing this is shown in Fig. 6, in which the ink 65 in the cells 60 is supplied through a tube 66 from an ink reservoir 61. After one cycle of printing is completed, the paper I0 is moved as indicated by arrow 1| and the transparency T2 is synchronously moved as indicated by the arrow 13. The valve is opened, allowing ink to flow into the cell 60, filling the capillary right down even with the orifice 62. The valve 15 is then closed, and the printing light, as indicated by arrows i6, is then turned on, for example by opening a shutter. This light passes through the transparency l2 and differentially heats up the cell 65 in accordance with the image in the transparency. This causes ink to be ejected from the orifice 62 and deposited on the paper 18, after which the cycle is repeated.

Figs. 7 and 8 show a slightly different embodiment of the invention in which the expansion cells 80 are on the top of a printing bar 8|, and

the capillaries 82 extend from the cells down through this bar to reach the printing surface 83. The upper surface of the cells is covered by transparent plate 84, and the supply channels 85 extend to the side of the bar 8|, whereat they alternately connect to and are out off from ink supply channels 81. These ink supply channels are carried in blocks 88, which are springurged against the bar 8| by springs 89. The periodic printing operation requires the bar 8| to be moved out of contact with the paper 83, and at the same time the ink channels 81 to be connected to the cells 80. In Fig. 8 the right hand side of the figure illustrates one part of the cycle, whereas the left hand illustrates another part of the cycle, and in practice both sidesare either in the up or in the down position at any one time. The motion of the various members is provided by means not shown in this particular figure. An alternative arrangement is shown in Fig. 9, which has the advantage that only the printing bar 9| need be moved. That is, the bar 9| is moved into contact with or very near the paper 92 for printing and the image light indicated by arrows 93 is turned on, expelling the ink from the cells 94 through the orifices 95. The bar 9| is then raised out of contact with the paper bringing the cells 94 into contact with the supply reservoirs 96, during which time the light 93 is cut oif by a suitable shutter. This operation is illustrated in perspective in Fig. 10 wherein light from a lamp me illuminates a narrow band |0| of a transparency H32. This line of light is focused by a lens ||l3 on the upper surface 91 of the printing bar 9 l, causing ink to be printed on the paper 92. The light is then cutoff by a shutter I84, and simultaneously the printing bar 9| is raised by a cam I05 coupled to the shutter I04 to move synchronously therewith. The cam 3-5 is to one side of the paper web 92 so that it raises only the printing bar l9 and does not raise the paper at the same time. This raising of the printing bar 9| bring the expansion cells into contact with the ink supply Hit, which is supplied through channels 96. At the same time the transparency I02 and the paper 92 are moved forward the width of the scanning slit. Then the cam ||J5 lowers the printing bar 9| into contact with the paper, the shutter I04 opens and light falling on the surface 91 causes the ink to print on the paper, after which the cycle is repeated. The transparency I02 is shown flat for clarity, but in practice it is wrapped on a cylinder so that the printing operation is continuously repeated making a large number of prints on the roll of paper 92.

Before describing preferred embodiments in which the expelling medium is different from the ink being expelled, I wish to point out how the rate of operation of the invention is computed for the simple ink filled cells illustrated in Figs. 5 to 10. The following data is given for a 300 line per inch picture and for a printing source which in the exposure time allowed gives a 5 C. rise in temperature through the least dense portion of the negative, that is, the maximum temperature increase is 5 C.

The volume of each cell such as shown in Fig. 5 is approximately .006" x .010" x .004", which when converted to cubic centimeters equals 3.'Z5 10- cc. Thus from each cell containing an alcoholic ink about l.9 l0* cc. of ink is expelled. The total volume of ink expelled from the 2100 cells comprising a seven 7 inch line, not counting the differential reduction due to the density of the image is about l lO cc. The heat absorbed by a single cell to raise the temperature of the alcohol 5 C. is about 9 10 calories which in turn works out to .019 calories for the 2100 cells.

These figures correspond to the usual amount of ink deposited in printing. That is, the maximum ink expelled from a cell is equivalent to a square of ink .003 x .003 x .0001".

The length of the capillary which is emptied when this ink is expelled depends of course on the diameter of the capillary and also on the expansion thereof. For example, a capillary .00004" in diameter will expel a length of ink equal to 0.8 inch whereas one .0003 in diameter will only expel .016 of ink from the tube. Although a long capillary travel favors accurate rendering of density variations, it is easier to make the larger diameter capillaries. The capillaries need not be highly regular or uniform in section. Thus without going to inconveniently intense light sources, it is possible to cut exposure time per line to .001 second, but I prefer to use somewhat less intensity and slightly longer printing time,

The coefficient of expansion of inks is not as high as that of certain other liquids, solids, and particularly gases. Therefore, for higher speed operation, I prefer to use a gaseous medium in the expansion cells. One arrangement for doing this is illustrated in Fig. 11, wherein the expansion cell I I0 is normally at atmospheric pressure when the valve III is open as shown and the shutter H2 is closed so that no light from the object II3 through the lens II4 falls on the cell surface II5. In this condition the capillary II'I connected to the cell H0 is also connected to an ink reservoir II8, which is at atmospheric pressure since the valve H9 is open. The capillary attraction of ink from the reservoir H3 to the orifice I2I is augmented by a slight vacuum applied through a valve I22 and an overflow pipe I23 right at the orifice. Preferably this vacuum is arranged so as to bring the ink quickly down to the orifice but not sufiicient to draw off any appreciable amount of ink during this operation. The valves III, H9, and I22 are then all closed and the shutter II2 opened so that the image falls on the expansion cell IIO. Since the valves are all closed, the expansion of the gas in the cell III] forces ink from the orifice I2I onto the printing paper I25. The cycle is then repeated by closing the shutter H2 and opening the three valves.

This gas cell type of printing is applicable to the printing press shown in Fig. by using an arrangement such as shown in Fig. 12. During printing, light as indicated by arrows I passes through a transparent or heat transmitting plate I3I to cause the medium in the cells I32 to expand, forcing ink from the orifices I33. The printing bar I34 is down during this operation so that the supply tubes I35 are cut off by the face I35 of the ink supply channels I31. After the printing part of the cycle is completed, the bar I34 is raised away from the paper to the position indicated by the broken lines I38, In this position the cells I32 are connected directly to the atmosphere through openings I39 and the capillaries are connected through tubes I35 to the ink supply I40 in the ink supply channels I31.

There are many ways in which the small cells may be manufactured, but one of the least expensive and most satisfactory methods involves printing and electroforming of a matrix, from which the cells are cast by simple molding operations. Such an arrangement is illustrated in Figs. 13 to 16. A base plate I45 is first printed by any suitable printing method with a spot I46 and a line I41 of a conducting medium, such as silver. Photographic processes may be used for depositing the silver as a spot and a line corresponding to each cell. The silver is then copper plated by electrolytic deposition until the line is built up to a height equal to the desired capillary thickness, as illustrated by I48 in Fig. 14. The plate I45 is then withdrawn from the electrolytic solution to the point indicated by broken line I50, so that only the spot I46 remains in the solution. Copper deposition is continued until a high bump I49 is formed on each spot I46. This matrix, consisting of plate I45 and the copper pattern formed thereon, is then coated with a suitable transparent plastic I5I, which covers the strip I48 but does not quite cover the top of the bump I49. If any plastic does coat on the bumps I49, this is removed by a light hand-buffing before the plastic is stripped from the mold. A pair of such strips I52, after being stripped from the mold, are placed in register so that an expansion cell I53 is formed, corresponding to the holes through both strips, and the capillary I54 is formed by the line in the upper of the two strips. These strips are then cemented securely to a plate I55, which has been perforated with a row of perforations I55 corresponding to the cells. The front surface of the cell is covered by a transparent strip I51 cemented to the bottom of the lower strip I52. The cement I58 used in this case is suflicient to fill the small groove I59, which exists in the lower strip by reason of its similarity to the upper strip in which the corresponding groove forms the capillary required. One eminently satisfactory way of assuring register between the plate I55 and the strips I52 is shown in Fig. 16 in which the plate I55 is made first and the plate I45 is made from it photographically by exposing through the orifice I56 on to a photosensitive layer I60. The exposure at the point I6I is continued until a considerable size spot is fogged and then the plate I45 is moved steadily and fairly fast under the orifice I56 so that lines leading from each spot to the edge of the plate are exposed, eventually to form the lines I41.

Fig. 1'7 is included to show a zig-zag arrangement of the expansion cells I65 and a corresponding zig-zag arrangement of the orifices I66. With this, arrangement the cells completely cover the length of the scanning line. That is, the width of the cell I61, as indicated by broken lines I58, is exactly equal or even slightly greater than the space between the cells I69. Too much overlapping would reduce the definition of the finished print, whereas too much space between the cells reduces the efficiency of the printer.

Figs. 18 and 19 illustrate a four-color printer for printing simultaneously, according to the present invention, from four color separation transparencies I15. These four transparencies are carried by an Invar belt I16, which is driven by rollers I11 over a series of rollers I18, all inside a large housing I80. Where the color separation transparencies are all film, the preferred method of assuring proper register is to register all of the films one on top of the other and then to perforate all four of them. The films are then mounted on the belt I16 by properly located pins carried by the belt I16. Alternatively, and preferably, glass plates are used for the color separation records, and in this case the plates are provided with registration marks shown as crosses I8I in Fig. 20, which registration marks are accurately located with respect to perforations I82 in the Invar belt I16. The plate as indicated by broken lines I83 is then clamped in place by suitable clamps I84. The registration of the lower two transparencies I is advanced relative to that of the upper two to allow for the offset of the corresponding printing stations 2 to be described later.

The purpose of using Invar as the supporting belt is to insure maintenance of register throughout a long run of, say, 5,000 prints, by avoiding temperature effects on the length of the belt. The four color separation records I15 are illuminated a line at a time by two lamps I90 and I91. From each side of each lamp a beam of light passes through a spherical lens I92 and a cylindrical lens I93 to be reflected from a plane mirror I94 and to form a line of light I95 on the color separation record I15. The housing I80 is shielded from each lamphouse by windows I91. These windows I91 may have a predetermined relative density or may be in the form of density wedges to permit color balance adjustment of the printer. The intensity of the lamps are controlled respectively by rheostats 200 and I. Photoelectric cells 202 and 203 are provided adjacent to each lamp to permit accurate control of the relative intensity of the two lamps throughout the printing operation. The connections to these photoelectric cells are not shown since they are not an essential part of the present invention, but the control may be either manual operation of the rheostats 200 and 2M in accordance with meter readings, or may be automatic. The lamphouses are cooled by fans 205 and an insulation layer 206 is provided to keep the heat of the lamphouse from unnecessarily being transmitted to the printing chamber.

Light from the color separation records I15 is then focused by lenses 2l0 to form a line of light on rows of juxtaposed expansion cells 2, in accordance with the invention. The lenses 2I0 are shown as simple positive elements for clarity, but actually, highly corrected lenses are used. The details of the expansion cells 2 are so small that they cannot appear in this Fig. 18 but such details are illustrated in Figs. 5 to 12. A supply roll 220 of a transparent pellicle feeds a strip of material between two pairs of the ink depositing units 2. A motor 22I through a gear 222 and gears 223 and 224 synchronously drives the pellicle 225 and the Invar belt I16. Two colors are deposited on each side of the pellicle which then passes over a diagonal roller 230 and out of the box through an aperture provided therein, particularly as shown in Fig. 19. Usually an illuminator 23I as shown by broken lines in Fig. 19 is provided for quick inspection of the picture 232 on the pellicle as it passes from the printer.

After each print is made the Invar belt is returned to the starting position by disengaging the gear 224 from the gear 222. In the arrangement shown, this is performed manually, but a simple direct gearing arrangement may be employed for quickly driving the Invar belt I16 back to its starting position between the making of successive prints. Furthermore, in the arrangements shown relatively quick drying inks are used which permit the use of rollers engaging the full width of the pellicle. Obviously rollers which engage only the edges of the pellicle are used with more slowly drying inks. The pellicle, after inspection, is laminated to any opaque white support desired, such as paper. To permit a new set of color separation negatives to be mounted on the Invar belt I10 and to permit a new supply roll 220 of pellicle to be inserted, the wall 240 of the housing I is removable as indicated by attaching screws 2.

Having thus described the preferred embodiments of my invention, I wish to point out that it is not limited to these structures but is of the scope of the appended claims.

I claim:

1. The method of reproducing a picture which comprises filling with ink a line of juxtaposed capillary orifices in a solid block, each connected to a fluid-filled cell, the cells also being in line, illuminating a line of a negative of the picture in printing relation to the line of cells, exposing the cells by light from the line of the negative to heat the cells thereby causing expansion of the fluid and emission of ink from the orifices, receiving the emitted ink on an ink receptive support, and periodically replenishing the capillary orifices with ink while synchronously scanning the negative by the line which exposes the cells and the support by the line of orifices.

2. The method according to claim 1 in which said fluid in the cells is solely ink, contiguous with the ink in the capillary orifices.

3. A printing device comprising a block containing a plurality of small juxtaposed ink filled cells each including an ink filled capillary extending to an orifice in the printing surface of the block, the orifices forming one and at most two single straight lines, means for filling the cells with ink, means for closing the cells completely except for said capillaries and means for exposing the so closed cells to a line of an infrared image.

4. A printing device comprising a block containing a plurality of small juxtaposed fiuid filled cells each having a capillary extending to an orifice in the printing surface of the block, at least the part of the fluid in the capillary being ink, the orifices forming one and at most two single straight lines, means for filling the cells with ink, means for closing the cells completely except for said capillaries and means for exposing the so closed cells to a line of an infrared image.

5. A printing device according to claim 4 in which the fluid in the cells is partly the ink and partly gas and in which there is means for supplying ink to the capillaries other than through the gas-filled portions of the cells.

ALEXANDER MURRAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,709,926 Weaver Apr. 23, 1929 1,770,493 Ranger July 15, 1930 1,817,098 Ranger Aug. 4, 1931 1,957,646 Hinton May 8, 1934 2,143,376 Hansell Jan. 10, 1939 2,278,940 Murphy Apr. 7, 1942 2,370,160 Hansell Feb. 27, 1945 2,413,706 Gunderson Jan. 7, 1947 

